DESCRIPTION (Verbatim from applicant's abstract): The proposed research will examine how the cellular mechanisms of the retina operate together as a neural circuit to process visual information. Emphasis is placed on how population activity of retinal ganglion cells can be accounted for by a description of the cellular and synaptic mechanisms of other retinal circuit elements. The light responses of retinal interneurons will be monitored by intracellular recording while simultaneously recording activity in about 50 ganglion cells using a multi-electrode array. Intracellular stimulation will reveal how the synaptic output of interneurons affects the responses of ganglion cells. The morphology of retinal interneurons will be measured and correlated with their functional output to ganglion cell activity. The specific retinal processes that will be examined are the synaptic connections that produce correlated firing of ganglion cells, the cellular mechanisms of adaptation to contrast and spatial scale, and the influence of amacrine cells on ganglion cell activity. Because a description of how cellular elements combine together to produce population activity is not clear in the retina or any other neural system, this research will reveal basic principles of functional neural circuitry and may provide a framework to detect and characterize defects in visual processing.